Vacuum drive assembly

ABSTRACT

A drive assembly ( 10 ) to drive packaging film for delivery to a packaging machine. The assembly ( 10 ) includes an elongated endless flexible belt ( 11 ) with a plurality of teeth ( 16 ) that are used to drive the belt ( 11 ). The teeth ( 16 ) are arranged in rows along the longitudinal edges of the belt ( 11 ). Between the rows of teeth ( 16 ) is a row of apertures ( 23 ) that communicates with a gallery ( 20 ).

TECHNICAL FIELD

The present invention relates to vacuum drive assemblies and more particularly but not exclusively to vacuum drive assemblies used to move tubular bag material to a packaging machine.

BACKGROUND OF THE INVENTION

Described in U.S. Pat. No. 4,663,917 is a packaging machine. The packaging machine receives tubular bag material into which product is delivered, with the packaging machine then transversely sealing and transversely cutting the tubular bag material to provide bags of product. The tubular bag material is moved to the packaging machine by a vacuum drive assembly (film drive unit). Vacuum belt drive assemblies (film drive assemblies) are disclosed in U.S. Pat. Nos. 7,472,528 and 4,910,943.

Film drive units include a gallery past which a belt is driven. A vacuum is applied to apertures in the belt so that the packaging film is moved into contact with the belt so as to be gripped by the belt. Accordingly as the belt is driven, the tubular bag material is moved with the belt for delivery to the packaging machine.

A disadvantage of known film drive units is that as the belts wear air leaks into the galleries thereby reducing the vacuum applied to the apertures in the belt. This has the disadvantage that the packaging film is not securely engaged with the result that bags may not be correctly fanned by the packaging machine.

OBJECT OF THE INVENTION

It is the object of the present invention to overcome or substantially ameliorate at least one of the above disadvantages.

SUMMARY OF THE INVENTION

There is disclosed herein a vacuum drive assembly including:

-   -   a gallery to which reduced air pressure is to be applied, the         gallery having at least one aperture;     -   an endless belt engaged with the gallery so as to be movable         past the gallery in a predetermined direction, the belt having a         longitudinally extending inner surface and a longitudinally         extending outer surface between which apertures extend, the         apertures being located at longitudinally spaced locations along         the belt and are to be aligned with the gallery aperture so that         reduced air pressure is applied to apertures of the belt aligned         with the gallery aperture, a plurality of drive teeth located at         spaced locations along the inner surface to be engaged by a         drive sprocket that is to drive the belt in said direction, the         projections being arranged in a pair of parallel rows, the rows         each extending longitudinally of the belt but being transversely         spaced so that the belt apertures are located between the rows;         and wherein     -   said gallery has a pair of elongated guide projections located         between the teeth and engaged with the inner surface to aid in         sealingly connecting the inner surface to the gallery, with the         teeth also engaging the projections so that the belt is guided         thereby in passing the gallery.

Preferably, said gallery aperture is a slot extending in said direction.

Preferably, the drive teeth are arranged in pairs, each pair consisting of a tooth from each of the rows, with teeth of each pair being transversely aligned, with a belt aperture located therebetween.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred form of the present invention will now be described by way of example with reference to the accompanying drawings wherein:

FIG. 1 is a schematic parts exploded isometric view of a vacuum drive belt and a vacuum gallery;

FIG. 2 is a schematic isometric exploded view of portion of the belt of FIG. 1;

FIG. 3 is a schematic side elevation of the gallery and belt of FIG. 1 with drive sprockets;

FIG. 4 is a schematic sectioned side elevation of the gallery and belt as shown in FIG. 3 sectioned along the line 4-4; and

FIG. 5 is a schematic enlarged view of portion of the gallery and belt as shown in FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the accompanying drawings there is schematically depicted a vacuum drive assembly 10. Typically the assembly 10 would drive packaging film to be delivered to a packaging machine. As a particular example, two assemblies 10 could be provided, with the assemblies 10 being located on opposite sides of tubular bag material being delivered to the packaging machine.

The assembly 10 includes an elongated endless flexible belt 11. The belt 11 includes a longitudinally extending body 12 having an outer longitudinal surface 13 and a longitudinally extending inner surface 14. Extending between the surfaces 13 and 14 is a plurality of belt apertures 15.

Extending inwardly from the surface 14 is a plurality of drive teeth 16. The teeth 16 are arranged in a pair of rows 17 that extend longitudinally of the belt and are transversely spaced so as to be adjacent the edge portions of the belt 11. The teeth 16 are arranged in pairs that are transversely aligned across the belt so that an aperture 15 is located therebetween.

The belt 11 is driven in a predetermined direction 18 by a pair of drive sprockets (rollers) 19. Each of the drive sprockets 19 has a plurality of teeth that engage the teeth 16 so as to drive the belt 11 in the direction 18.

Engaged with the belt 11 is a gallery 20. The gallery 20 includes an enclosed chamber 21 that via a duct 22 is connected to an air pump that reduces the air pressure in the chamber 21.

The gallery 20 also has a longitudinally extending slot (aperture) 23 that extends in the direction 18. The aperture 23 is located so as to communicate with a selected number of the apertures 15 that are aligned with the aperture 23.

Located on either side of the aperture 23 are longitudinally extending guide projections 24. The guide projections 24 are located between the rows 17 so as to slidably engage the internal surfaces 25 of the teeth 16 to guide the belt 17 in its movement past the gallery 20.

Each of the projections 24 has a generally planar longitudinally extending sealing surface 26 that slidably engages the inner face 14 of the belt 11 to sealingly connect the gallery 20 to the belt 11. In this regard it should be appreciated that the aperture 23 is closed at its end extremities.

An advantage of the above described preferred embodiment is that the surfaces 26 engage the surface 14 so that a reduced air pressure is applied to the apertures 15. This arrangement is more tolerant to wear of the surfaces 26 and 14. Additionally the belt is urged into contact with the gallery as a result of the reduced air pressure at the inner surface 14. 

1. A vacuum drive assembly including: a gallery to which reduced air pressure is to be applied, the gallery having at least one aperture; an endless belt engaged with the gallery so as to be movable past the gallery in a predetermined direction, the belt having a longitudinally extending inner surface and a longitudinally extending outer surface between which apertures extend, the apertures being located at longitudinally spaced locations along the belt and are to be aligned with the gallery aperture so that reduced air pressure is applied to apertures of the belt aligned with the gallery aperture, a plurality of drive teeth located at spaced locations along the inner surface to be engaged by a drive sprocket that is to drive the belt in said direction, the projections being arranged in a pair of parallel rows, the rows each extending longitudinally of the belt but being transversely spaced so that the belt apertures are located between the rows; and wherein said gallery has a pair of elongated guide projections located between the teeth and engaged with the inner surface to aid in sealingly connecting the inner surface to the gallery, with the teeth also engaging the projections so that the belt is guided thereby in passing the gallery.
 2. The assembly of claim 1, wherein said gallery aperture is a slot extending in said direction.
 3. The assembly of claim 1, wherein the drive teeth are arranged in pairs, each pair consisting of a tooth from each of the rows, with teeth of each pair being transversely aligned, with a belt aperture located therebetween.
 4. The assembly of claim 2, wherein the drive teeth are arranged in pairs, each pair consisting of a tooth from each of the rows, with teeth of each pair being transversely aligned, with a belt aperture located therebetween. 